Molecular beam epitaxial growth of III-V semiconductor ... - KOBRA

Heteroepitaxial Growth of III-V Semiconductor on Silicon Substrates
stress and strain introduced by mismatched system and crystal defects. The purpose
of this chapter is to review the properties and challenges of the epitaxial
integration of III-V semiconductors on silicon substrates that bear on these aspects
of heteroepitaxy, including crystallographic properties, elastic properties,
surface properties as well as the dierent types of structural defects.
3.2 The Concept of Epitaxy
The term "epitaxial" is applied to a lm grown on top of the crystalline substrate
in ordered fashion that atomic arrangement of the lm accepts crystallographic
structure of the substrate. Epitaxial growth is one of the most important
techniques to fabricate various "state of the art" electronic and optical devices.
Modern devices require very sophisticated structures, which are composed of thin
layers with various compositions. Quality, performance and lifetime of these devices
are determined by the purity, structural perfection and homogeneity of the
epitaxial layers [31]. Epitaxial crystal growth resulting in epitaxial layer perfection,
surface atness and interface abruptness depend on a number of factors like:
The epitaxial layer growth method, the interfacial energy between substrate and
epitaxial lm, as well as the growth parameters - thermodynamic driving force,
substrate and layer mist, substrate misorientation, growth temperature, etc.
Recently epitaxial growth is used intensively for the fabrication of semiconductor
quantum structures like quantum dots giving highly perfect structures with high
density.
3.2.1 Fundamental Processes During Epitaxy
Regardless of the growth technique, atoms and molecules are delivered to the
substrate surface, and a large fraction of these species adsorb on the surface. Once
adsorbed, there are three things that can happen to an adatom. It can either form
a strong chemical bond to the surface where it is trapped, diuse on the surface
to nd an energetically preferred location prior to strong chemical bonding or
desorb. Once adsorbed chemically, the adatoms can diuse on the surface and
this diusion can be highly anisotropic, depending on the symmetry and nature of
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